The present invention relates to a floating point data adder for adding and subtracting two floating point input data having mantissas thereof expressed in a sign-magnitude format, and more particularly to a floating point data adder which produces a sum or difference of mantissas of two data in an expression of a sign-magnitude format.
In a floating point data adder with input data having mantissas thereof expressed in a sign-magnitude format, an addition/subtraction mode of the mantissa data is specified only by signs of the input data and a specified operation mode. Accordingly, an operation result of the mantissa data may become negative in a one's or two's-complement format, and in such a case the result must be converted to a sign-magnitude format. Accordingly, when such adders are configured in a pipeline, the number of pipeline stages is larger than that of a one's or two's-complement pipelined floating point data adder as shown in U.S. Pat. No. 4,075,704. In other words, an additional stage is required to express the mantissa data by the sign-magnitude format after the arithmetic operation. As a result, it is inevitable that the performance of the scalar operation is deteriorated by an overhead due to the additional stage.